Fiber optic transceivers are used in a variety of applications, including storage area networks (SANs), local area networks (LANs), Fibre Channel, Gigabit Ethernet, and synchronous optical network (SONET) applications. Fiber optic transceivers can be used as the network interface in mainframe computers, workstations, servers, and storage devices. Fiber optic transceivers can also be used in a broad range of network devices, such as bridges, routers, hubs, and local and wide area switches.
Fiber optic transceivers include a fiber optic receiver and a fiber optic transmitter. The fiber optic receiver converts optical serial data to electrical serial data and the fiber optic transmitter converts electrical serial data to optical serial data. A majority of fiber optic transceivers include power control circuits, diagnostic circuits, and other circuits for enhancing the functionality of the fiber optic transceivers.
Fiber optic transmitters include a transmitter optical subassembly (TOSA). Typically, TOSAs include a laser diode and a monitor diode. Temperature variations during operation of TOSAs affect the tracking error (TE) and the slope efficiency (SE) of the TOSAs. These variations may vary from TOSA to TOSA. This may require an individual temperature compensation of each TOSA for each fiber optic transceiver.
Average power (Pave) and extinction ration (ER) vary with temperature due to laser parameter changes over temperature. Pave can be controlled by varying the setting of a first potentiometer that changes the bias current to the laser diode as the temperature changes. ER can also be controlled over temperature by varying the setting of a second potentiometer that changes the modulation current as the temperature changes.
All lasers do not behave identically; therefore one temperature compensation curve for the first potentiometer and a one temperature compensation curve for the second potentiometer cannot be used to compensate for all lasers. Typically, the values for the first potentiometer and the second potentiometer are found by iteratively searching for values to provide the desired Pave and ER at every few degrees within the operating temperature range of the laser. Interpolation between the values is used to create a profile or curve for the first potentiometer and the second potentiometer that can be determined to keep Pave and ER within specification.